For development, I use the NetBeans IDE*, which includes the Swing GUI Builder.
You can also download and install the NetBeans Profiler for diagnostics.
There is also the NetBeans™C/C++ Pack 5.5 which enables C/C++ coding and compiling, but I have not yet used it for compiling the QCamJNI.c code for CamAcqJ.
(A NetBeans Project for CamAcqJ development will be published soon… )
* I have not used Eclipse enough to say if it is better or worse than NetBeans. But I can say that when I tried to try it, I found it hard just to get my project running (I had been using JBuilder). I found it much easier to get started with NetBeans, and using the JBuilder project importer, was able to get my code running very quickly. Overall, I think Eclipse and NetBeans a comparable, but my personal preference is NetBeans.

NetBeans 5.5 IDE
I have built a NetBeans Project configured for ImageJ Plugin Development.
ijNB package
Download You can download it from here. ijNB.zip (2.7M)

Create a directory for the project (say ijNB) and extract the contents of the zip (using subfolders).
Open the project with NetBeans.
To Update to the Latest ImageJ Source Code
(As of January 2, 2007, this package contains the ImageJ source version 1.38f)
When new versions of ImageJ are released:
Download ijXXXx-src.zip
Unzip it… this creates a folder: source
Replace the ImageJ source code In the directory where you installed ijNB